1. Field of the Invention
This invention relates to an improved process for reducing water content of raw mix slurries used in the manufacture of cement by the wet process.
2. Description of Prior Art
In the manufacture of cement by the wet process, a slurry of the raw mix is pumped through pipes into the kiln where water is evaporated and the raw mix calcined to obtain Portland cement. It is desirable to reduce the water content of the raw mix slurry without increasing or altering the viscosity of the slurry. Numerous processes using chemical compositions as water reductants in raw mix slurries have been proposed. For example, U.S. Pat. No. 2,709,661 - Dietz - issued May 31, 1955 describes reduction of water in raw mix slurries by the use of alkali metal salts such as alkali metal polyphosphates, alkali metal polythiophosphates, alkali metal polysilicates, alkali metal polymolybdates, alkali metal polyvanadates, or alkali metal salts of polyboric-polyphosphoric acid in conjunction with a salt of methylene naphthalene sulfonic acid and sufficient sodium carbonate to adjust the pH of the slurry to 6.5 - 9.5.
The salt of methylene naphthalene sulfonic acid described in the above patent is a member of the class of alkyl naphthalene sulfonates having two or more naphthalene rings joined by methylene groups. The formula for methylene naphthalene sulfonic acid is: ##SPC1## Other members in this class are of indefinite composition and are manufactured by heating naphthalene, formaldehyde and sulfuric acid together or by heating naphthalenesulfonic acid with formaldehyde. In this manner, three or more naphthalene rings may be joined together by methylene groups to obtain a low molecular weight condensation polymer.
Sodium salts of sulfonated naphthaleneformaldehyde condensates are used as extensively as dispersing agents for pigments and are classified as surfactants. These condensates are offered under a variety of names and are well known in the art. They have been described by a variety of chemical names such as the sodium salt of a condensed mononaphthalene sulfonic acid, sodium salt of a sulfonated naphthalene formaldehyde condensate, sodium salt of condensed naphthalene sulfonic acid and sodium naphthaleneformaldehyde sulfonate.
Even though the process described in the above patent reduces the moisture content of the slurry, there is a definite need for improved additives.